Air pollution can kill

WASHINGTON - A growing body of evidence shows that air pollution is linked with heart attacks, strokes and cardiovascular deaths.

People, particularly those at high cardiovascular risk, should limit their exposure, says an updated American Heart Association (AHA) scientific statement.

The evidence is strongest for fine particulate matter (PM2.5) having a causal relationship to cardiovascular disease, said the expert panel of authors who updated the AHA 2004 initial statement on air pollution.

There are several ways by which PM2.5 could affect the cardiovascular system; however, one leading explanation suggests that several components of PM2.5, once inhaled, can cause inflammation and irritate nerves in the lungs.

These responses can start a cascade of changes that adversely affect the rest of the body, Brook said. “It’s possible that certain very small particles, or chemicals that travel with them, may reach the circulation and cause direct harm,” said Robert D. Brook, associate professor of internal medicine University of Michigan (U-M), Ann Arbor.

“The lung nerve-fibre irritation can also disrupt the balance of the nervous system throughout the body. These responses can increase blood clotting and thrombosis…, elevate blood pressure, and disrupt proper cardiac electrical activity which may ultimately provoke heart attacks, strokes, or even death,” said Brooks.

The major source of PM2.5 is fossil fuel combustion from industry, traffic, and power generation. Biomass burning, heating, cooking, indoor activities and forest fires may also be relevant sources, particularly in certain regions.

“Particulate matter appears to directly increase risk by triggering events in susceptible individuals within hours to days of an increased level of exposure, even among those who otherwise may have been healthy for years,” said Brook, lead author of the statement.

It was written after review of epidemiological, molecular and toxicological studies published during the past six years.

“Growing evidence also shows that longer-term PM2.5 exposures, such as over a few years, can lead to an even larger increase in these health risks,” said Brooks.

“The foremost message for these high-risk groups remains that they should work to control their modifiable traditional risk factors - blood pressure, cholesterol, diabetes, smoking,” said Brook, associate professor of internal medicine at the University of Michigan (U-M), Ann Arbor.

“These studies also indicate that there is no ’safe’ level of PM2.5 exposure,” he said, according to an U-M release.

Recommendations include: Physicians should emphasise treatment of traditional cardiovascular risk factors, which may lessen patients’ susceptibility to air pollution. Patients with cardiovascular disease should be educated about the risks of air pollution.

These findings were also published in Circulation: Journal of the American Heart Association.